Despite all the negative replies, I agree... I didn't care for the whole "X's are cool" act, All that made me think of was a dad trying to be "trendy" for a group of kids so he can be seen as such a 'cool' guy.

Yeah, but with the others they were serious a lot.
With Smith he just seemed to go overboard on the eccentricity.
It just got to the point where it's like "OK, enough"
The others did it as well, but Eccleston was like an eccentric Business man, Tennant was like a teacher, Smith just seemed like the class clown.

I'm sure there's some detailed explanation about emotions and stuff that make him like that but I don't wanna go into it and besides, who cares, he's gunna regenerate, and we'll get a new mature doctor so everyone can be happy. Excluding the rabid fan girls who no one cares about anyway.